This invention relates to touch sensitive controls for electrical apparatus and especially multiple input, touch sensitive controls to be used in wet or dirty environments.
There are numerous situations where electrical equipment such as motors, lights and heaters are to be controlled (turned on and off) through some type of control panel from a central location. A good example is found in spa pools and hot tubs. Usually, due to water and chemicals, the environment around a control panel is quite hostile to standard electrical control panels using devices such as toggle switches, membrane switches and potentiometers. Clearly the need exists for a control panel whose electrical components need not be exposed to the local environment, whether chlorinated water from a spa pool or chemicals and dirt from an industrial site.
U.S. Pat. No. 4,651,023 offers a partial solution to the stated problem in that light sensitive resistors (photoresistors) are enclosed in a water tight container and activated by blocking ambient light passing through clear windows in the container. A pair of photoresistors are required for each function in order to form an effective switch; one photoresistor is covered to establish the "on" condition and the other photoresistor is covered for "off". This arrangement is not particularly well suited for systems where many functions are to be controlled from a single panel, due to the large number of photoresistors that would be required, as well as the large number of support components such as operational amplifiers, resistors and capacitors that would be needed.
An objective of the present invention is to provide a control panel that can be operated by selectively touching, or approaching, touch sensitive senors mounted under a clear protective cover. Another objective is to use only one sensor for each function to be controlled, so that each subsequent touch will toggle the function "on" or "off", depending on the last state.
A final objective is to use only a small number of supporting components in the control panel to minimize size and cost and to maximize reliability.